Ultrasound promoted regioselective synthesis of beta-iodoethers from olefin-I2-alcohol

Regioselective synthesis of β-iodoethers in high yields by sonicating alkene and alcohol in the presence of iodine in a bath at 35 kHz is reported.     

Ultrasound promoted synthesis of thioesters from 2-mercaptobenzoxa(thia)zoles

An ultrasound-enhanced method has been developed for the synthesis of a variety of thioesters from benzoyl chlorides and 2-mercaptobenzoxa(thia)zoles. Applying this methodology, 14 compounds were synthesized in excellent yields.     

Microwave spectrum of 2-aminopyridine

The microwave spectra of 2-aminopyridine-NH₂, -ND₂, and of both of the two possible -NHD molecules have been observed and assigned in the 0⁺ vibrational state of the amino group inversion vibration; the assignment for three of the molecules in the 0⁻ state is also made. From intensity measurements the 0⁺-0⁻ splitting is estimated to be 135 ± 25 cm⁻¹ for the -NH₂ molecule and 95 ± 30 cm⁻¹ for the -ND₂ molecule. The rotational constants are interpreted in terms of a structure in which the amino group is bent about 32° out of the molecular plane, the c coordinates of the two amino H atoms being 0.21 and 0.28 Å. Stark effect measurements give a dipole moment of about 0.9 D which is almost entirely in the b axis, and which changes quite significantly between the 0⁺ and 0⁻ states.     

Ultrasound promoted synthesis of 2-aroyl-1,3,5-triaryl-4-carbethoxy-4-cyanocyclohexanols

Synthesis of 2-aroyl-1,3,5-triaryl-4-carbethoxy-4-cyanocyclohexanols from chalcones with ethyl cyanoacetate is carried out in excellent yields with KF/basic alumina as catalyst under ultrasound irradiation.     

Ultrasound promoted synthesis of Nile Blue derivatives

Ultrasound irradiation was used for the first time towards the synthesis of new Nile Blue related benzo[a]phenoxazinium chlorides possessing isopentylamino, (2-cyclohexylethyl)amino and phenethylamino groups at 5-position of the heterocyclic system. The efficacy of sonochemistry was investigated with some of our earlier reported synthesis of benzo[a]phenoxazinium chlorides. This newer protocol proved competent in terms of reaction times and enhanced yields. Photophysical studies carried out in ethanol, water and simulated physiological conditions, revealed that emission maxima occurred in the range 644–656 nm, with high fluorescent quantum yields. Other attractive feature exhibited by these materials includes good thermal stability. These properties might be useful in the development of fluorescent probes for biotechnology.     

Ultrasound promoted synthesis of some novel fused pyrans

Novel fused pyrans were synthesized from the reaction of the tetrahydropyran-4-one with arylidine malononitriles. Different fused pyran derivatives were obtained from the mentioned reaction depending on type of catalyst used and type of energy used. Reactions were carried out under silent and ultrasonic conditions. In general, it was found that sometimes ultrasound irradiations change the reaction path in comparing with silent condition. In addition to improvement in reaction times, the products were obtained in high yields and their structures were determined by elemental analyses, spectral data.     

Ultrasound promoted facile synthesis of arylhydrazones at ambient conditions

Arylhydrazones have been synthesized in excellent yields in short reaction times at ambient temperature conditions in the absence of any added catalyst by the reaction of phenylhydrazines with carbonyl compounds under ultrasonic irradiation.     

Ultrasound promoted synthesis of substituted pyrazoles and isoxazoles containing sulphone moiety

Novel pyrazoles and isoxazoles were synthesized from the reaction of the carbanions of 1-aryl-2-(phenylsulphonyl)-ethanone with different hydrazonyl halides and 1-aryl-2-bromo-2-hydroximinoethanone in ethanol, respectively. Reactions were carried out under silent and ultrasonic conditions. In general, it was found that ultrasound irradiations enable some reactions to occur which could not be carried out under silent condition in addition to improvement in reaction times. The products were obtained in high yields and their structures were determined by elemental analyses, spectral data and X-ray diffraction.     

Metal free synthesis of homoallylic alcohols promoted by ultrasound

The use of ultrasound irradiation to promote the allylation of aldehydes containing different functionalities with potassium allyltrifluoroborates is described. The method features the use of a minimum amount of acetone as solvent, without any other catalyst or promoter. The products were obtained in high yields, short reaction times, at room temperature and without the need of further purification.     

Ultrasound promoted clay catalyzed efficient and one pot synthesis of substituted oxindoles

A simple facile, one-pot synthesis of oxindoles in reasonable purity is reported via intramolecular Friedal-Craft cyclization. Clay KSF is an inexpensive, efficient and mild catalyst for the synthesis of substituted oxindoles by the reaction of chloroacetyl chloride and various anilines under the influence of ultrasonic irradiation under solvent-free conditions. The remarkable advantages of this method are the simple experimental procedures, short reaction times, high yields of products, suitability for a wide variety of substituents, and the green aspects through the avoidance of toxic catalyst and solvents.     

Millimeter wave measurement and assignment of the rotational spectrum of 2-aminopyridine

Previous work involving the rotational spectrum of 2-aminopyridine was limited to the lower frequencies of 4-40 GHz with very few lines being assigned. This work extends this earlier study. Here we present a much more extensive measurement and assignment of the rotational spectrum of 2-aminopyridine in the frequency range of 75-110 GHz. The observed frequencies have been assigned to the ground (0⁺ state) and the first excited state in the inversion vibration (0⁻ state). Measurements of these two states have been extended up to J=46. With the newly assigned lines, significantly improved rotational constants and all five centrifugal distortion constants have been obtained.     

Ultrasound promoted one-pot synthesis of 3-aza-6,10-diaryl-2-oxa-spiro[4.5]decane-1,4,8-trione

One-pot synthesis of 3-aza-6,10-diaryl-2-oxa-spiro[4.5]decane-1,4,8-trione from 1,5-diaryl-1,4-pentadien-3-one can be carried out in good yields at 50 °C under ultrasound irradiation. This method provided several advantages such as simple work-up procedure, shorter reaction time and higher yield.     

Cyclohexyl iodide promoted approach for coumarin analog synthesis using small scaffold

New chemical approaches were adopted for the synthesis of biologically important coumarins utilizing cyclohexane-1,3-dione derivatives as novel scaffold which were prepared from acetone and ethyl acrylate following our previous report. The stepwise strategies of aromatization, dehydrogenation, and demethylative cyclization were followed for coumarins synthesis from cyclohexane-1,3-dione derivatives. This work reports the first time cyclohexyl iodide was used for the demethylative cyclization reaction of $\upbeta , \upbeta $ -diaryl acrylates for 4-arylcoumarins synthesis. Graphical abstract      

Enhanced rate of carbon deposition during fischer-tropsch synthesis on K promoted Fe

The synthesis of hydrocarbons from CO and H₂ at 1 bar pressure was measured on a Fe foil which was previously covered with a monolayer of K₂CO₃. The surface composition of the K promoted Fe was monitored repetitively by interrupting the reaction and transfering the sample into the UHV chamber for X-ray photo-emission spectroscopy. The results show that K causes a decrease in the rate of methane formation, an increase, in the rate of carbon deposition, and a shift in selectivity towards the formation of longer chain molecules. The XPS measurements on the K 2p levels show furthermore that the K compound is apparently not being covered by the deposited carbon but rather sitting on top of the carbon layer.     

2-氨基吡啶气相氟代反应的密度泛函理论研究

采用量子化学方法,运用密度泛函理论(DFT)B3LYP方法,在6-311G*基组水平上,以2-氨基吡啶为起始反应物,全优化计算了亚硝酰阳离子NO~+对2-氨基吡啶中氨基进攻的重氮化反应及氟硼酸根阴离子BF_4~-对吡啶重氮正离子进攻的席曼反应的机理,搜索到整个反应过程中的过渡态结构,得到了反应路径并通过IRC验证,并对各反应中间体、过渡态和产物进行分子几何构型优化、振动频率分析和标准热力学函数计算.通过计算,搜索到的过渡态均为环状结构,与配位插入反应类似,利于原子间化学键的断裂及新键的形成;通过热力学及动力学计算,重氮化-席曼反应是剧烈的放热反应,与实验结果相吻合.     

Ultrasound promoted ZrCl(4) catalyzed rapid synthesis of substituted 1,2,3,4-tetrahydropyrimidine-2-ones in solvent or dry media

Sonication of aromatic aldehydes, urea and ethyl acetoacetate in presence of solvent (ethyl alcohol) or solvent-less dry media (bentonite clay) supported-zirconium (IV) chloride (ZrCl(4)) as catalyst at 35 kHz gives 6-methyl-4-substitutedphenyl-2-oxo-1,2,3,4-tetrahydropyrimidine-5-carboxylic acid ethyl esters proficiently in high yields.     

Ultrasound promoted synthesis of 5-hydroxy-5-trihalomethyl-4,5-dihydroisoxazoles and beta-enamino trihalomethyl ketones in water

A convenient method for the preparation of 5-hydroxy-5-trihalo-4,5-dihydroisoxazoles and beta-enamino trihalomethyl ketones, from the reaction of 1,1,1-trihalo-4-alkoxy-3-alken-2-ones with hydroxylamine and anilines, respectively, using water as solvent and under ultrasound irradiation is reported.